Normal: "Once the most powerful of all fiends. With the coming of more formidable Weapons it has relinquished that title, but it remains a mighty adversary nonetheless." Oversoul: "Even more powerful in its oversouled form. It appears to be highly cognitive. For example, when attacked with magic, it considers how to respond." — Scan
Omega is a powerful adversary, as it can inflict Itchy with its normal attack, and hit the entire party with its powerful Judgment attack. It is highly advisable to set up Protect at the start of the fight and hit it with the best attacks each party member is capable of using.
Omega Weapon is the final opponent of the Demon Cup. If the player manages to defeat him, they will be given a choice to either recruit Ultima or Omega Weapon. If they choose Omega Weapon, he will join the party. Upon completing his storyline, Almighty Shinra is created and Demon Cup becomes Shinra's Cup.
Even after recruiting Almighty Shinra, the player can reopen Shinra's Cup by viewing Omega Weapon's ending in the Creature Creator.